1. Field of the Invention
The present invention relates to a linear vibrator, and more particularly, to a linear vibrator achieving stable linear vibrations by preventing vibrations in a horizontal direction.
2. Description of the Related Art
In recent years, a personal mobile terminal having a large liquid crystal display (LCD) screen for a user's convenience has been increasingly released onto the market. In line with this trend, a touch screen type display device has been greatly favored, and a vibration motor has been used so as to generate vibrations when a touch is applied to a touch screen.
A vibration motor transforms electrical energy into mechanical energy using a principle of generating electromagnetic force, is mounted on a personal mobile terminal, and is used for silent call reception notification.
According to the related art, rotatory power is generated to rotate a rotational part of an unbalance mass, thereby obtaining mechanical vibrations. In this case, rotatory power is generated such that it is subjected to a rectifying action through a brush and a contact point of a commutator (or rectifier) to obtain mechanical vibrations.
However, in the brush type structure using a commutator, when the motor rotates, the brush passes through a gap between segments of the commutator, causing mechanical friction and an electrical spark, producing foreign objects and thereby shortening the life span of the motor.
In addition, because voltage is applied to the motor by using a moment of inertia, time is taken to reach a target amount of vibrations, so it is difficult to implement vibrations suitable for a touch screen.
In order to overcome such disadvantages in terms of the life span and response of the motor and implement the vibration function of the touch screen, a linear vibrator is increasingly being used.
A linear vibrator, rather than using the rotational principle of the motor, uses the following principle: when electromagnetic force, obtained by using a spring installed inside a vibration motor and a mass body hung on the spring, is generated periodically in conformity with a resonance frequency, resonance is caused, thereby generating vibrations.
However, in a case in which the mass body performs an abnormal operation or unstable vibrations due to an external impact, this impact affects the coupling portion of the spring and the mass body, and accordingly this may cause defects such as disconnection of a coil. A vibration unit including the spring or the mass body may be separated from its preset position.
Therefore, techniques for preventing impact induced by an external force to generate stable linear vibrations are required. Also, a study for a linear vibrator capable of stopping vibrations quickly and stably is urgently needed.